The present disclosure is directed to assembly and installation of cassette housings for circuit cards disposed therewith. More particularly, the present disclosure is directed to snap-fit assembly of circuit card cassettes having the ability to assemble the cassettes without tools or trained personnel. Such cassettes find use in a variety of different applications. For example, such cassettes find particular use in the area of circuit boards.
The past twenty-five or so years have seen the development of ever smaller electrical circuit components at the chip level. However, to take fullest advantage of achievements in electrical circuit miniaturization, one must package the resultant printed circuit cards containing these chips in an efficient manner. Clearly, the packaging of printed circuit cards in tight spaces is a direct logical extension of increasing chip level circuit densities. It should also be noted that the tight packaging of integrated circuit chips on printed circuit cards and the correspondingly dense packaging of the printed circuit cards is a design goal that is carried out for more than just the convenience of compactness. Compactness provides shorter distances between circuit components which, in turn, serves the very desirable goal of being able to operate the circuits effectively at higher frequencies, thus increasing the speed of numerous different forms of electrical systems, including but not limited to data processing systems.
Moreover, mainly for reasons associated with long-term system operation and reliability, it is likewise very desirable to be able to easily insert and remove these printed circuit cards even when they are disposed in very tight spaces. The insertion and removal operations are also provided as an important part of a xe2x80x9chot-pluggabilityxe2x80x9d function which is very desirable for xe2x80x9con the flyxe2x80x9d repairs, replacements, maintenance and upgrades.
With increased circuit density there has also been a concomitantly driven increase in the number of power, signal and control lines which require electrical connections to be made between printed circuit cards and printed circuit boards. This means that the electrical connectors that carry these various electrical circuits between the cards and the boards have been required to carry more and more separate individual connections. A significant consequence of the increase in the number of individual electrical connections, all of which require surety of contact, is the corresponding increase in the force needed to insert printed circuit connectors into mating printed circuit board sockets. This aspect provides special design considerations for self contained cartridges that carry printed circuit cards which are meant to be inserted into printed circuit boards via actuating mechanisms contained within the cartridge itself.
The increase in the number of connections also poses other problems in the design of desirably compact packaging systems, particularly those designed for easy cartridge insertion and removal. In particular, the increased number of connections results in the use of connectors with an increased number of pins and socket holes. Since these structures are present in larger and larger numbers, the pin-and-socket connections (or the like) are themselves packed together with smaller and smaller distances between them. This aspect of the packaging problem brings along with it the problem of connecting pin alignment for the purpose of physically connecting oppositely disposed mating pins and socket holes. Alignment failure can severely and permanently damage both the printed circuit card and the printed circuit board into which the card is to be inserted.
Also of note is the fact that one of the principle purposes of the present invention is to provide cartridges which are capable of this self contained insertion actuation function. Even more particularly, the present invention employs cartridges which are designed to have no physical contact with any external structure except the printed circuit board itself. This means that cartridges of the present invention do not require any form of actuation mechanism which relies upon external structures such as an enclosure, cabinet or frame or upon any form of adaptation provided in a surrounding cabinet, frame or enclosure.
As an additional constraint on packaging design, it should be appreciated that, with increased circuit density, there is also a concomitant increase in power density and heat dissipation. Accordingly, packaging designs should be fully compatible with those aspects of system design associated with cooling functions. Also, to whatever extent possible, packaging designs should be: economical to produce; function smoothly; require little or no maintenance; be producible from inexpensive, readily available materials; and be reliably operable over a large number of insertion and removal operation cycles.
Yet one other concern arises in electrical systems as circuit feature size shrinks, operating frequencies increase and packaging densities grow larger, namely, the generation of electromagnetic interference (EMI). Electronic circuit packaging designs should thus also be compatible with structures and configurations that are employed to prevent the leakage of electromagnetic interference. To whatever extent possible, packaging designs should also include structures which actually contribute positively to the containment of electromagnetic interference.
It is also noted that the present discussion refers to printed circuit boards and printed circuit cards. As contemplated herein, the printed circuit board is the larger component into which at least one printed circuit card is inserted for purposes of electrical connection. The present disclosure places no specific limits on either the size of a printed circuit board or the size of a printed circuit card. In the most general situation, a circuit board will be populated with a plurality of printed circuit cards. That is, the printed board will have a number of printed circuit cards inserted therein. Accordingly, as used herein, the terms xe2x80x9cprinted circuit boardxe2x80x9d and xe2x80x9cprinted circuit cardxe2x80x9d are considered to be relative terms.
Accordingly, the present inventors are presented with the following sometimes competing packaging problems: connector pin alignment, cartridge alignment, rigid connection to a printed circuit board, dense and close packaging, cooling, electromagnetic interference shielding, hot pluggability, the desire to provide an easy-to-load and easy-to-assemble cartridge for carrying printed circuit cards, and mechanisms requiring a mechanical advantage for insertion and removal of printed circuit cards.
A pluggable cartridge for inserting a circuit card into an enclosure without operator access to the enclosure interior is provided. The cartridge includes a top portion and a first wall configured to secure the circuit card thereon for movement in unison therewith and a second wall. The first and second walls have a bottom edge and a top edge wherein the top edge of the first wall is movably secured to the top portion. The top edge of the second wall is removably secured to the top portion by snap-fit means. The circuit card is housed within and protected by the first and second walls so as to be moveable with respect to the bottom edge of the second wall. A tail stock bezel is removably secured by snap-fit means at one end of the second wall and top portion. A handle is movably connected to the top portion so as to be movable between a first position and a second position. A portion of the handle is operably attached to the first wall by an articulated mechanical linkage such that movement of the handle to the first position causes the printed circuit card secured to the first wall to move to a position proximate the bottom edge. Movement of the handle to the second position causes the printed circuit card to move to a position remote from the bottom edge.
A method of snap-fit assembly of a pluggable cartridge having a circuit card secured thereto without requiring the need for any tools is also provide. The method includes adjustably securing the circuit card to a first wall of a card holder assembly movably coupled to a top portion. The card holder assembly is configured to secure the circuit card thereon for movement in unison therewith. The method further includes engaging a second wall with said top portion for snap-fit engagement, the second wall having a bottom edge and a top edge and removably securing the top edge of the second wall to the top portion by snap-fit means. The circuit card is housed within and protected by the first and second walls assembly so as to be moveable with respect to the bottom edge of the second wall. A tail stock bezel is slid on from the bottom edge to the top edge at one end of the second wall and the top portion and removably secured by said snap fit means at one end of the second wall and top portion. A handle is movably connected to the top portion so as to be movable between a first position and a second position, a portion of the handle is operably attached to the card holder assembly by an articulated mechanical linkage such that movement of the handle to the first position causes the circuit card to move to a position proximate the bottom edge and such that movement of the handle to the second position causes the printed circuit card to move to a position remote from the bottom edge.